From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Wed, 5 May 2021 20:25:24 +0000 (+0200)
Subject: netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5e024c325406470d1165a09c6feaf8ec897936be;p=linux.git

netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check

Do not assume that the tcph->doff field is correct when parsing for TCP
options, skb_header_pointer() might fail to fetch these bits.

Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index e8f8875c6884e..0fa2e20304272 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -186,6 +186,8 @@ static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
 
 		ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
 				sizeof(struct tcphdr), ctx->optsize, opts);
+		if (!ctx->optp)
+			return NULL;
 	}
 
 	return tcp;